Technical Field
The present invention generally relates to the field of audio data processing. More particularly, the present invention relates to an adaptive jitter buffer for buffering audio data received via a packet-switched network. Furthermore, the present invention relates to a device for receiving audio data, comprising the adaptive jitter buffer.
Description of the Related Art
Introduction
Voice-over-internet-protocol (VOIP) telephony allows flexible realizations of communication applications since the access to the transport medium is no longer restricted by telephone companies: VOIP terminals can be realized as softphones on PCs, laptops, and mobile handheld devices, such as smartphones, as long as an internet access is provided that allows to access the world-wide-web (WWW) as the transport medium to connect people all over the world.
However, in comparison to conventional telephony applications over public-switched-telephone-networks (PSTNs), the flexibility of the transport medium WWW comes at the price of new challenging technical problems, which may be solved by engineers for ensuring a high quality VOIP communication.
In conventional telephony over PSTNs, for many years, a so-called circuit-switched transport medium has established a channel was exclusively reserved for a specific connection between two communicating partners. Data transmitted by one partner reached the other partner via a deterministic connection with well-known temporal delay and negligible data loss rates.
These days, in VOIP, media data—that is, in most cases at least audio data, but often also video data—is transmitted in packets, which contain data for short time periods, via an internet-protocol (IP) link, often denoted as packet-switched networks. No channel is exclusively reserved and no route is known in advance, such that the connection cannot be considered as being deterministic any longer. Even worse: often adjacent packets produced by VOIP terminals follow different routes and in many cases cross different network topologies—denoted as heterogeneous networks. However, various drawbacks can result from the use of non-deterministic transmission links.
In practice, many problems in a VOIP communication application caused by the non-deterministic nature of the transport medium are the so-called network jitter as well as frame losses. The technological functionality that addresses both problems in VOIP terminals is the adaptive jitter buffer described in the following.